The wall barrier is shaped towards the potential impact of the vehicle with a particular sequence of three different slopes.
They have the task of moving the impacting wheel in such a way that first the vehicle ascends on the so shaped face (creating the acceleration absent in blade type and stake barriers) and then send it back towards the roadway that had abandoned, in a time more or less longer depending on the angle and speed of impact. If the energy of the impact is higher, the barrier has also a displacement that dissipates energy by friction. The displacement of the wall barrier gives rise to a loop, more or less accentuated, in the protection line. It induces the vehicle to flow along the barrier and not to bounce towards the center of the road, as happens in elastic collisions without movement.

This effect, combined with the mechanism of ups and downs already described, facilitates control of the trajectory and redirection, especially for vehicles of greater mass.
The least damages to cars in respects to impacts against metal barriers, is instead due to up and down mechanisms.